Substrate cleaning method for removing oxide film

ABSTRACT

It was found out that when radicals generated by plasma are fed to a treatment chamber via a plurality of holes ( 111 ) formed on a partition plate which separates a plasma-forming chamber ( 108 ) from the treatment chamber, and the radicals are mixed with a treatment gas which is separately fed to the treatment chamber, the excitation energy of the radicals is suppressed and thereby the substrate surface treatment at high Si-selectivity becomes possible, which makes it possible to conduct the surface treatment of removing native oxide film and organic matter without deteriorating the flatness of the substrate surface. The radicals in the plasma are fed to the treatment chamber via radical-passing holes ( 111 ) of a plasma-confinement electrode plate ( 110 ) for plasma separation, the treatment gas is fed to the treatment chamber ( 121 ) to be mixed with the radicals in the treatment chamber, and then the substrate surface is cleaned by the mixed atmosphere of the radicals and the treatment gas.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation application of PCT InternationalApplication No. PCT/JP2008/067016, filed on Sep. 19, 2008, the entirecontents of which are incorporated by reference herein.

This application also claims the benefit of priority from PCTInternational Application No. PCT/JP2007/071393 filed Nov. 2, 2007, theentire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an apparatus and a method ofmanufacturing semiconductor device, including the treatment of substratesurface, specifically the treatment of surface of group IVsemiconductor.

Related Background Art

Conventionally semiconductor Si substrate is subjected to wet-cleaning.The wet-cleaning has, however, problems of failing to completely removewater-marks in dry state, failing to control etching of very thin oxidefilm, requiring large apparatus, and the like. Furthermore, when thesemiconductor substrate is exposed to atmospheric air for a long timeafter the wet-cleaning, there arise problems of forming native oxidefilm on the surface thereof and adsorbing carbon atoms thereon toinhibit film-forming of Si single crystal, generating irregular profileof film, generating impurity level at the interface of gate insulationfilm, and the like.

Therefore, surface oxide film was removed by applying UHV vacuum heatingto 750° C. or higher or by applying heating to 800° C. or higher in anH₂ atmosphere before film formation. However, as miniaturization ofdevice progresses and dielectric insulation film/metal electrode isused, the device needs to be manufactured at lower temperatures. Thusthe device manufacturing needs to be done at 650° C. or lowertemperature. As a result, the wet-cleaning has its limits, and therearises a need of dry-cleaning method which conducts treatment ofsemiconductor substrate in a vacuum before film-forming. The reversesputtering method using argon plasma is one example of the method(Japanese Patent Laid-Open No. 10-147877). The disclosed method,however, presumably cuts also the Si—Si bond on the surface of thesemiconductor substrate. In that case, problems arise such that oxidefilm is immediately formed on the Si-absent portion, that contaminantslikely adhere to the dangling bond of Si, and that the sputtered oxideand contaminants adhere again to the side wall of the substrate. Theseproblems adversely affect the succeeding step, (such as inhibition ofepitaxial growth and formation of highly resistant portion on thesilicide interface). Furthermore, damages on the device are also theproblem.

Japanese Patent Laid-Open No. 2001-144028 describes that, after removingthe silicon oxide film from the surface of the substrate using aplasmatized F₂ gas, the hydrogen radicals are irradiated to remove the Fcomponent adhered to the surface of the substrate. Japanese PatentLaid-Open No. 04-96226 describes that, after removing the Si nativeoxide film from the surface of the substrate using F₂ gas, theradicalized hydrogen is irradiated to the substrate to terminate thebonding operation by the hydrogen. Japanese Patent Laid-Open No.06-120181 discloses a technology of terminating the bonding operation byhydrogen on the surface of the substrate using hydrogen ions afterremoving the oxide film on the substrate surface by HF plasma. Since,however, the plasmatized F₂ gas contains not only the radicalizedfluorine gas but also the ionized fluorine gas. There arises a problemof generating irregular surface on removing the silicon oxide film fromthe substrate surface. Furthermore, there is a possibility of removing aportion of the substrate itself not only removing the silicon oxide filmthereon. In addition, since the semiconductor substrate is exposed toplasma, Si—Si bond is also cut off. In that case, there arise problemsthat the oxide film is immediately formed on the Si-absent portion, thatthe contaminants likely adhere to the dangling bond of Si, and that thesputtered oxide and contaminants adhere again to the side wall of thesubstrate. These problems adversely affect the succeeding stage, (suchas inhibition of epitaxial growth and formation of highly resistantportion on the silicide interface). Furthermore, damages on device arealso the problem. According to the disclosure, gas is decomposedpositively by plasma to generate hydrogen radicals and hydrogen ions.When fluorine residue on the surface of the substrate is removed by thehydrogen radicals and the hydrogen ions, there arise problems ofcontamination by metal coming from the chamber, of excess etchingbecause of large etching rate on the base Si, and the like. Furthermore,since HF as the reaction product likely adheres again to the surface ofthe substrate, sufficient F-removal effect is not attained.

Japanese Patent Laid-Open No. 2001-102311 describes that a cleaning gassuch as fluorine is supplied to the plasma-forming part having theplasma-forming chamber which is separated, by a plate having feed holestherethrough, from the film-forming chamber where the substrate isplaced, thus generating radicals by generating plasma in theplasma-forming part, and the fluorine radicals are fed to thefilm-forming space containing the substrate via the feed holes, therebyirradiating the radicals to the substrate for cleaning thereof. JapanesePatent Laid-Open No. 2002-500276 discloses a substrate cleaning methodusing a plate distributing the gas excited by a remote plasma source,through which plate the radicals are supplied to clean the substrate.Since, however, the surface of the semiconductor substrate cannot beexposed to an atmosphere which suppresses the excitation energy ofradicals, etching with high Si selectivity cannot be conducted, whichthen raises a problem of failing to remove the native oxide film withoutdeteriorating the surface roughness.

Japanese Patent Laid-Open No. 2002-217169 discloses an apparatus forconducting entire cleaning step in a vacuum to remove foreign matterapplying simultaneously a physical action of friction stress generatedby a high velocity gas flow. According to the disclosure, adsorption ofimpurities and generation of native oxide during vacuum transfer aresuppressed, thus improving the production efficiency. Even if theforeign matter can be removed, however, the native oxide film and thesurface roughness remain on the surface at an order of atomic layerthickness. That is, to attain the effect of device characteristicimprovement by the continuous transfer in vacuum, there are required thecleaning technology to control the highly selective etching of Si andnative oxide film at an order of atomic layer thickness, and thetransfer of substrate and the film-forming thereon without exposing thesubstrate to atmospheric air. That kind of control technology and vacuumoperation should provide good device characteristics of low interfacestate at the joint between semiconductor and dielectric insulation film,and of small fixed charge in the film.

Japanese Patent Laid-Open No. 10-172957 describes that the oxide filmwas able to be selectively removed by a mixed gas of: argon, helium,xenon, and hydrogen which are excited by a remote plasma source; and HFgas fed in downstream side, and that no damage was observed on thesilicon substrate. The removal, however, did not satisfy the flatnessrequired in recent years.

[Patent Document 1] Japanese Patent Laid-Open No. 2001-144028

[Patent Document 2] Japanese Patent Laid-Open No. 04-96226 (1992)

[Patent Document 3] Japanese Patent Laid-Open No. 06-120181 (1994)

[Patent Document 4] Japanese Patent Laid-Open No. 2001-102311

[Patent Document 5] Japanese Patent Application Publication No.2002-500276

SUMMARY OF INVENTION Problems to be Solved by the Invention

According to the conventional wet-cleaning surface treatment to removenative oxide film and organic matter from the substrate surface, thereis a problem of deteriorating the device characteristics owing to theadsorption of air components to the substrate surface to leave nativeoxide film and impurities such as carbon atoms on the interface becausethe substrate after cleaned is transferred to the succeedingfilm-forming step in atmospheric air. When the substrate after treatedby dry-cleaning on the surface thereof is subjected to the treatment ina vacuum not to leave the native oxide film and the impurities such ascarbon atoms on the interface, the flatness of the substrate surface isdeteriorated caused by the dry-cleaning, though the native oxide filmand the impurities such as organic matter and carbon on the substratesurface can be removed. Furthermore, poor flatness of the substratesurface raises a problem of deteriorating the characteristics ofmanufactured device.

Means to Solve the Problems

The present invention is made to solve the above problems. According tothe investigations of the inventors of the present invention, radicalsgenerated by plasma are fed to the treatment chamber via a plurality ofholes formed on a partition plate which separates the plasma-formingchamber from the treatment chamber, the radicals are mixed with atreatment gas which is separately fed to the treatment chamber, thussuppressing the excitation energy of the radicals to thereby enable thesubstrate surface treatment at high Si-selectivity, and thus it is foundout that the surface treatment becomes available which removes nativeoxide film and organic matter without deteriorating the flatness of thesubstrate surface.

The present invention provides a method of cleaning a substratecomprising the steps of: placing a substrate in a treatment chamber;turning a plasma-forming gas; feeding a radical in the plasma to thetreatment chamber via a radical-passing hole of a plasma-confinementelectrode plate for plasma separation; feeding a treatment gas to thetreatment chamber to mix it with the radical in the treatment chamber;and cleaning the surface of the substrate by the mixed atmosphere of theradical and the treatment gas.

The present invention provides a method of cleaning a substrate, whereinthe surface of the substrate is a group IV semiconductor material, andthe plasma-forming gas and the treatment gas contain HF, respectively.

The HF fraction in the plasma-forming gas to the total gas flow rate ofthe plasma-forming gas is preferably in a range from 0.2 to 1.0, andmore preferably from 0.5 to 1.0. The HF fraction in the treatment gas tothe total gas flow rate of the treatment gas is preferably in a rangefrom 0.2 to 1.0, and more preferably from 0.75 to 1.0.

The present invention provides a method of cleaning a substrate, whereinthe plasma-confinement electrode plate for plasma separation has aplurality of radical feed holes for feeding the radical in the plasma tothe treatment chamber and a plurality of treatment gas feed holes forfeeding the treatment gas into the treatment chamber, and thus theradical and the treatment gas are discharged toward the surface of thesubstrate in the treatment chamber via the respective feed holes.

The present invention provides a method of manufacturing a semiconductordevice comprising the steps of: cleaning the surface of a group IVsemiconductor substrate in a cleaning chamber in accordance with theabove method; transferring the cleaned substrate from the cleaningchamber to an epitaxial chamber via a transfer chamber without exposingthe substrate to atmospheric air; and epitaxially growing an epitaxialsingle crystal layer on the surface of the substrate in the epitaxialchamber.

The present invention provides a method of manufacturing a semiconductordevice comprising the steps of: transferring a substrate having anepitaxial layer manufactured in accordance with the above method fromthe epitaxial chamber to a sputtering chamber via a transfer chamberwithout exposing the substrate to atmospheric air; sputtering adielectric film onto the epitaxial layer in the sputtering chamber;transferring the substrate having the dielectric film thereon from thesputtering chamber to an oxidation-nitrification chamber via a transferchamber without exposing the substrate to atmospheric air; andconducting oxidation, nitrification, or oxynitrification of thedielectric film in the oxidation-nitrification chamber.

The present invention provides a method of manufacturing a semiconductordevice according to above method, wherein the dielectric film is made ofthe one selected from the group consisting of Hf, La, Ta, Al, W, Ti, Si,and Ge, or an alloy thereof.

The present invention provides a method of cleaning a substrateaccording to above method, wherein turning the plasma-forming gas intoplasma is done by applying a high frequency power thereto, and thedensity of the high frequency power is in a range from 0.001 to 0.25W/cm², preferably from 0.001 to 0.125 W/cm², and more preferably from0.001 to 0.025 W/cm².

The present invention provides a substrate treatment apparatus ofplasma-separation type generating a radical by forming plasma from aplasma-forming gas in a vacuum chamber, and conducting substratetreatment by the radical and a treatment gas, the substrate treatmentapparatus comprising: a plasma-forming chamber for turning theplasma-forming gas fed therein into plasma; a treatment chambercontaining a substrate holder on which a substrate to be treated isplaced; and a plasma-confinement electrode plate for plasma separationhaving a plurality of radical-passing holes formed between theplasma-forming chamber and the treatment chamber, the plasma-confinementelectrode plate of a hollow structure having a plurality of treatmentgas feed holes opened toward the treatment chamber formed, and having agas-feed pipe for supplying the treatment gas disposed, wherein: aplasma-forming space inside the plasma-forming chamber contains ahigh-frequency applying electrode for generating plasma by a powersupplied from a high-frequency power source; the high-frequency applyingelectrode has a plurality of through-holes penetrating therethrough; thehigh-frequency applying electrode further contains a plasma-forming gasfeed shower plate for feeding the plasma-forming gas to theplasma-forming chamber; and the plasma-forming gas feed shower plate hasa plurality of gas-discharge ports for feeding the plasma-forming gasonto the electrode extending along the plasma-confinement electrodeplate for plasma separation provided with the plurality ofradical-passing holes.

The present invention provides a substrate treating apparatus, whereinthe diameter of the plurality of gas holes opened on the plasma-forminggas feed shower plate is 2 mm or smaller, and preferably 1.5 mm orsmaller.

The present invention provides a substrate treating apparatus, whereinin the above substrate treating apparatus, the volume ratio V2/V1 is ina range from 0.01 to 0.8, where V2 is the total volume of a plurality ofthrough-holes of the electrode, and V1 is the total volume of theelectrode including the through-holes.

The present invention provides a substrate treating apparatus accordingto above apparatus, wherein the density of the high frequency powerapplied to the high-frequency applying electrode is in a range from0.001 to 0.25 W/cm², preferably from 0.001 to 0.125 W/cm², and morepreferably from 0.001 to 0.025 W/cm².

The present invention provides a substrate treating apparatus accordingto above apparatus, wherein the plasma-forming gas fed to theplasma-forming chamber is a gas containing HF, and the gas fed to thetreatment chamber is a gas containing HF.

The present invention provides an apparatus of manufacturingsemiconductor device comprising: a substrate cleaning chamber includingthe above substrate treatment apparatus; an epitaxial growth chamberforming an epitaxial layer on the substrate; and a transfer chambertransferring the substrate coming from the substrate cleaning chamber tothe epitaxial growth chamber without exposing the substrate toatmospheric air.

The present invention provides an apparatus of manufacturing asemiconductor device according to above apparatus, further comprising asputtering chamber forming a dielectric film, thus allowing transferringthe substrate coming from the cleaning chamber or the epitaxial growthchamber to the sputtering chamber via the transfer chamber withoutexposing the substrate to atmospheric air.

The present invention provides an apparatus of manufacturing asemiconductor device according to above apparatus, further comprising anoxidation-nitrification chamber for oxidation, nitrification, oroxynitrification of the dielectric film, thus allowing transferring thesubstrate coming from the cleaning chamber, the epitaxial growthchamber, or the sputtering chamber to the oxidation-nitrificationchamber via the transfer chamber without exposing the substrate toatmospheric air.

Effect of the Invention

The present invention performs substrate treatment which can decreasethe native oxide film and organic impurities on the surface ofsemiconductor substrate compared with the wet-cleaning in the relatedart, and can remove the native oxide film and organic matter withoutdeteriorating the flatness of the substrate surface.

According to the present invention, to remove the native oxide film andcontamination of organic impurities from the surface of semiconductorsubstrate, HF gas or a mixed gas containing at least HF is used as theplasma-forming gas and the treatment gas, and radicals are fed from theplasma-forming chamber to the treatment chamber, while feedingsimultaneously gas molecules containing HF as the structural elementthereto, thus exposing the surface of semiconductor substrate to theabove atmosphere which suppresses the excitation energy of the radicals,to thereby remove the native oxide film and organic matter withoutdeteriorating the flatness of the substrate surface. There generates nometal contamination and plasma damage on the semiconductor substrate.Although the wet-cleaning in the related art needs more than one stepfor the substrate treatment applying also succeeding steps such asannealing treatment, the present invention performs the substratetreatment in only one step, which attains desired effect efficiently,reduces cost, and significantly improves the treatment speed.Furthermore, use of a shower plate to the plasma-forming gas allowsuniform feeding of the product gas, use of through-holes on theelectrode part allows discharge even at a low power, and use of aplasma-confinement electrode plate for plasma separation provided with aplurality of radical-passing holes allows radicals in the producedplasma to be fed uniformly to the treatment chamber. By using HF as theplasma-forming gas, feeding the radicals from the plasma-forming chamberto the treatment chamber, and simultaneously feeding HF to the treatmentchamber, the surface treatment provided fine surface roughness at anorder of atomic layer thickness, which then realized to form a singlecrystal Si and SiGe film on the surface.

By the first step of conducting substrate surface treatment, and thesecond step of transferring the substrate without exposing the singlecrystal film to atmospheric air, the amount of impurities at theinterface is smaller than that appears in the atmospheric transfer, andthus good device characteristics are attained.

By conducting the first step of conducting substrate surface treatment,the second step of forming single crystal film, the third step ofsputtering the dielectric material to form a film, the fourth step ofconducting oxidation, nitrification, or oxynitrification, and the fifthstep of transferring the metallic material and the sputtered film in avacuum without exposing thereof to atmospheric air, the amount ofimpurities on the joint interface between the semiconductor and theinsulation film becomes smaller than that in atmospheric transfer, whichprovides the interface state density and the fixed charge density infilm equivalent to those of oxide film attained in the related art,gives a C-V curve with small hysteresis, gives a small leak current, andthereby attains good device characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a configuration example of afilm-forming apparatus used in the present invention.

FIG. 2 is a schematic diagram of a controller installed in the apparatusused in the present invention.

FIG. 3A is a schematic diagram of a configuration example of a surfacetreatment apparatus used in the present invention.

FIG. 3B is an enlarged cross section diagram of a plasma-confinementelectrode plate in the surface treatment apparatus of the presentinvention.

FIG. 3C is an enlarged view of the plasma-confinement electrode plate inthe surface treatment apparatus of the present invention viewed from thetreatment chamber side.

FIG. 3D is a schematic diagram of the plasma-confinement electrode platepart of the present invention viewed from the treatment chamber side.

FIG. 4A is a schematic diagram of an example of structure of ahigh-frequency applying electrode part in the surface treatmentapparatus of the present invention.

FIG. 4B is a perspective view of an example of structure of thehigh-frequency applying electrode part in the surface treatmentapparatus of the present invention.

FIG. 4C is a diagram illustrating the generation of discharge in entiredischarge chamber under a condition of V2/V1 in a range from 0.01 to 0.8in the surface treatment apparatus of the present invention.

FIG. 4D is a diagram illustrating the state that, under a condition ofV2/V1<0.01, the discharge disproportionates, resulting in non-uniformradical supply to the substrate in the surface treatment apparatus ofthe present invention.

FIG. 4E is a diagram illustrating the state that, under a condition ofV2/V1>0.8, the discharge does not occur, thus the radical supply is notgiven to the substrate in the surface treatment apparatus of the presentinvention.

FIG. 5A is a schematic diagram illustrating an enlarged cross section ofa plasma-forming gas feed shower plate in the vicinity of aplasma-forming gas feed hole, showing a shape example 1 of theplasma-forming gas feed hole.

FIG. 5B is a schematic diagram illustrating an enlarged cross section ofthe plasma-forming gas feed shower plate in the vicinity of theplasma-forming gas feed hole, showing a shape example 2 of theplasma-forming gas feed hole.

FIG. 5C is a schematic diagram illustrating an enlarged cross section ofthe plasma-forming gas feed shower plate in the vicinity of theplasma-forming gas feed hole, showing a shape example 3 of theplasma-forming gas feed hole.

FIG. 5D is a schematic diagram illustrating an enlarged cross section ofthe plasma-forming gas feed shower plate in the vicinity of theplasma-forming gas feed hole, showing a shape example 4 of theplasma-forming gas feed hole.

FIG. 5E is a schematic diagram illustrating an enlarged cross section ofthe plasma-forming gas feed shower plate in the vicinity of theplasma-forming gas feed hole, showing a shape example 5 of theplasma-forming gas feed hole.

FIG. 5F is a graph of the distribution of etching rate of silicon oxidefilm in the plane of the substrate, showing the effect of the gas feedshower plate according to the present invention for feeding theplasma-forming gas to the plasma chamber.

FIG. 6 is a graph showing native oxide film/Si obtained in the examplesof the present invention with varied high-frequency power density.

FIG. 7 is a schematic diagram illustrating an example of structure of aUV, X-ray, and microwave excited radical surface treatment apparatusused in the present invention.

FIG. 8 is a schematic diagram illustrating an example of structure of acatalyst-chemical excitation radical surface treatment apparatus used inthe present invention.

FIG. 9 is a schematic diagram illustrating a surface treatment methodused in the present invention.

FIG. 10 is a flowchart of a transfer controller program used in thepresent invention.

FIG. 11 is a flowchart of a film-forming controller program used in thepresent invention.

FIG. 12 gives a graph showing the surface roughness (Ra) after treatmentof the substrate, and SEM images on the surface, obtained by an exampleof the present invention.

FIG. 13 is a graph showing the dependency of the surface roughness (Ra)on the HF fraction in the treatment gas, comparing the case ofplasma-forming gas containing HF according to the present invention withthe case of plasma-forming gas made only of Ar in the related art.

FIG. 14 gives SEM images on the surface after the growth of Si and SiGe,obtained by an example of the present invention.

FIG. 15 is a graph showing the atom density of oxygen and carbon atinterface, obtained by an example of the present invention.

FIG. 16 is a C-V curve obtained by an example of the present invention.

FIG. 17 is a graph showing a comparison of the interface state densityand the fixed charge density, between those obtained by an example ofthe present invention and those obtained in the related art.

FIG. 18 is a graph showing the relation between the equivalent oxidefilm thickness (EOT) and the leak current, obtained by an example of thepresent invention.

FIG. 19 is a schematic diagram illustrating a MOS-FET manufactured bythe treatment of the present invention.

EXAMPLES

Examples of the present invention will be described below.

Embodiments of the present invention will be described below referringto the drawings.

The examples deal with the cases of applying the present invention to afilm-forming apparatus 1 illustrated in FIG. 1, focusing on a process ofremoving a native oxide film and organic matter formed on a Si substrateby the first step using a surface treatment apparatus 100 illustrated inFIGS. 3A to 3D.

A substrate 5 adopted as the sample is a Si single crystal substrate(with 300 mm in diameter) which is allowed to stand in a clean air toform a native oxide film thereon. The substrate 5 is transferred to aload-lock chamber 50 by a substrate-transfer mechanism (not shown), andis placed therein. Then, the load-lock chamber 50 is evacuated by anevacuation system (not shown). After evacuating to a desired pressure,or 1 Pa or below, a gate valve (not shown) between the load-lock chamberand a transfer chamber is opened, and a transfer mechanism (not shown)in the transfer chamber transfers the substrate 5 to the surfacetreatment apparatus 100 via a transfer chamber 60, and places thesubstrate 5 on a substrate holder 114.

<Description of the Surface Treatment Apparatus>

FIG. 3A illustrates the surface treatment apparatus 100 of the presentinvention.

The surface treatment apparatus 100 includes a treatment chamber 113equipped with the substrate holder 114 on which the substrate 5 can beplaced, and a plasma-forming chamber 108. The treatment chamber 113 andthe plasma-forming chamber 108 are partitioned and separated from eachother by a plasma-confinement electrode plate 110 for plasma separationhaving a plurality of radical-passing holes 111 therein. Theplasma-confinement electrode plate 110 is made of a conductive materialand is grounded. The plasma-forming chamber 108 has a plasma-forming gasfeed shower plate 107 therein. A high-frequency applying electrode 104in a plate-shape is located between the plasma-forming gas feed showerplate 107 and the plasma-confinement electrode plate 110. Thehigh-frequency applying electrode 104 has a plurality of electrodethrough-holes 105 penetrating from the front face to the rear facethereof to uniformly stabilize the discharge. The high-frequencyapplying electrode 104 is connected to a high frequency power source 103and can supply high frequency power. The high-frequency applyingelectrode 104 is supported by an insulator 118 a and is fixed to thewall of the plasma-forming chamber as a plate-shape member extending ina lateral direction of the chamber in almost parallel with theplasma-confinement electrode 110. On both sides of the high-frequencyapplying electrode 104, there are upper and lower plasma-forming spaces109 a and 109 b, respectively.

The upper plasma-forming space 109 a contacts with the high-frequencyapplying electrode 104 and the plasma-forming gas shower plate 107. Thelower plasma-forming space 109 b contacts with the high-frequencyapplying electrode 104 and the plasma-confinement electrode plate 110.

FIG. 3B illustrates an enlarged cross section of the plasma-confinementelectrode plate 110. FIG. 3C illustrates an enlarged view of theplasma-confinement electrode plate 110 viewed from the treatmentchamber. As shown in these Figures, the plasma-confinement electrodeplate 110 faces the substrate-supporting face of the substrate holder114, and has the radical feed holes 111 penetrating from theplasma-forming space 109 to a substrate cleaning treatment chamber 121.The plurality of radical feed holes 111 are distributedly formed on theface of the electrode plate 110.

The plasma-confinement electrode plate 110 has a treatment gas feedpassage 120 to feed the treatment gas to the substrate cleaningtreatment chamber 121, treatment gas feed spaces 119, and gas feed holes112. The plurality of treatment gas feed holes 112 opened on theplasma-confinement electrode plate 110 toward the substrate cleaningtreatment chamber 121 from the treatment gas feed space 119 communicatedwith the treatment gas feed passage 120 of the plasma-confinementelectrode 110 are formed apposing to at least a part of the plurality ofradical feed holes 111 on the face of the plasma-confinement electrode110. The plasma-confinement electrode plate 110 has a hollow structureof the treatment gas feed passage 120 crossing laterally the electrodeplate 110, (in the direction of partitioning the plasma-forming chamber108 from the treatment chamber 113), and the treatment gas feed space119 through which the treatment gas is injected from the passage 120. Byfeeding the treatment gas to the treatment gas feed passage 120, thetreatment gas is uniformly supplied to the substrate 5 in the substratecleaning treatment chamber 121 via the plurality of treatment gas feedspaces 119 and via the plurality of treatment gas feed holes 112.

These treatment gas feed passage 120, treatment gas feed space 119, andtreatment gas feed hole 112 are not directly connected with theplasma-forming space 109 and the radical feed hole 111. Accordingly, theradicals fed from the radical feed holes 111 to the treatment space andthe treatment gas fed from the treatment gas feed holes 112 are fed fromthe plasma-confinement electrode face toward the substrate face in thesubstrate cleaning treatment chamber 121 in almost parallel flows witheach other. Then, the radicals and the treatment gas are mixed togetherin the substrate cleaning treatment chamber 121 for the first time.

The plasma-forming gas passes through a plasma-forming gas supply system101 and a plasma-forming gas supply pipe 102, and enters theplasma-forming space 109 a, the electrode through-holes 105, and theplasma-forming space 109 b in the plasma-forming chamber 108, viaplasma-forming gas feed holes 106 opened on the plasma-forming gas feedshower plate 107, and is raised to a specified pressure.

Once the power is supplied from the high frequency power source 103 tothe high-frequency applying electrode 104, discharge begins in the upperand lower plasma-forming spaces 109 a and 109 b. The plasma-confinementelectrode 110 functions as the ground electrode. Since theplasma-forming gas shower plate 107 also functions as the groundelectrode because the chamber wall of the plasma-forming chamber 108 towhich the plasma-forming gas shower plate 107 is connected is grounded.Grounding the plasma-confinement electrode plate 110 assures stabledischarge. Also grounding the plasma-forming gas shower plate 107assures stable discharge.

The shower plate may be an insulation material. In that case, thechamber wall positioned at a rear side thereof functions as the groundelectrode. The plasma-confinement electrode plate 110 partitions theplasma-forming chamber 108 from the substrate cleaning treatment chamber121. The substrate 5 being cleaned in the cleaning treatment chamber isplaced facing the plasma-confinement electrode plate face. The radicalsgenerated in the plasma in the plasma-forming spaces 109 a and 109 b arefed to the substrate cleaning treatment chamber 121 via the plurality ofradical feed holes 111 formed on the plasma-confinement electrode plate110 and communicating the plasma-forming chamber with the substratecleaning treatment chamber. The electrically neutral radicals areallowed to pass through the radical feed holes to enter the substratecleaning treatment chamber 121. However, very few of charged particlessuch as ions are allowed to pass through the radical feed holes 111formed on the plasma-confinement electrode plate 110. The radical feedholes 111 of the plasma-confinement electrode plate 110 confines theplasma, and allows the electrically neutral radicals to passtherethrough. By grounding the plasma-confinement electrode plate 110,the performance of confining the plasma and the performance of allowingthe electrically neutral radicals to pass therethrough are furtherimproved.

In addition, grounding the plasma-confinement electrode plate 110provides shielding not to leak high frequency to the substrate cleaningtreatment chamber 121. If the plasma-confinement electrode plate 110 isnot grounded, the high frequency applied to the high-frequency applyingelectrode 104 is not shielded by the plasma-confinement electrode plate110, and the plasma-confinement electrode plate 110 acts as theelectrode, which may induce discharge also in the substrate cleaningtreatment chamber 121 in the treatment chamber. Grounding theplasma-confinement electrode plate 110 can prevent the plasma invasionto and plasma generation in the substrate cleaning treatment chamber 121in the treatment chamber.

The unexcited treatment gas for suppressing the excitation energy of thefed radicals is fed from a treatment gas supply system 116 to thetreatment gas feed passage 120 via a treatment gas supply pipe 115 todiffuse therein, and then is fed to the treatment gas feed space 119,and further is fed to the substrate cleaning treatment chamber 121 viathe treatment gas feed holes 112.

The radicals fed from the radical feed holes 111 to the treatment spaceand the treatment gas fed from the treatment gas feed holes 112 aremixed together in the substrate cleaning treatment chamber 121 for thefirst time, to conduct specified treatment on the substrate 5 placedfacing the substrate cleaning treatment chamber 121.

After that, the gas in the substrate cleaning treatment chamber 121 isdischarged by an exhaust system 117.

The shape of the radical feed hole 111 is not limited to the oneillustrated in the drawings if only the hole has a function to allow theelectrically neutral radicals to pass therethrough and to reject theplasma from passing therethrough. For example, in FIG. 3B and FIG. 3C,the shape of the radical feed hole 111 has a larger diameter at the sidefacing the substrate cleaning treatment chamber 121 than the diameter atthe side facing the plasma-forming space 109. The diameter, however, maybe the same at both sides. Alternatively, the diameter thereof may besmaller at the side facing the substrate cleaning treatment chamber 121than the diameter facing the plasma-forming space 109. In FIG. 3B andFIG. 3C, the shape of the radical feed hole 111 has a spot-facing at theside of the substrate cleaning treatment chamber 121, with a narrow holeextended from the bottom of the spot-facing and opened toward theplasma-forming space. The number of narrow hole, however, may be morethan one. Furthermore, the spot-facing may be opened at the side of theplasma space, and a narrow hole may penetrate from the bottom of thespot-facing toward the treatment chamber, or the number of narrow holemay be more than one.

FIG. 3D is a schematic diagram illustrating the plasma-confinementelectrode plate 110 viewed from the treatment chamber side.

The radical feed holes 111 and the treatment gas feed holes 112 aredistributed and opened over the entire face of the plasma-confinementelectrode plate 110. Uniform distribution in the radius directionassures uniform supply of the radicals generated in the plasma-formingchamber toward the substrate, and assures uniform supply of thetreatment gas separately fed simultaneously toward the substrate.Compared with the case that the treatment gas is fed through a singlesupply pipe from, for example, a side wall of the substrate cleaningtreatment chamber 121, the structure of the present invention ofsupplying the treatment gas from the face of the plasma-confinementelectrode plate in parallel with the radical feeding is furthereffective in terms of not only the uniformity over entire surface of thesubstrate for cleaning treatment but also the selective etching ofnative oxide film to Si by suppressing excitation energy of theradicals.

The distribution of the radical feed holes 111 and the treatment gasfeed holes 112 is not limited to that given above, and the distributioncan be varied under a requirement of perfect uniformization of theintraplane distribution for the substrate treatment, such as to respondto the fluctuations in gas concentration ratio induced by the reactionof substrate treatment in the substrate cleaning treatment chamber 121.For instance, the distribution density of radical feed holes 111 may beincreased at peripheral area compared with that in central area, ordecreased in peripheral area compared with that in central area.Similarly, the distribution density of treatment gas feed holes 112 maybe increased at peripheral area compared with that in central area, ordecreased in peripheral area compared with that in central area. Inthose cases, the decrease or the increase in the distribution density ofradical feed holes 111 from the central area to the peripheral area maybe linear or exponential.

The plasma-forming gas passes through the plasma-forming gas supplysystem 101 and the plasma-forming gas supply pipe 102, and enters theplasma-forming space 109 in the plasma-forming chamber 108 via theplasma-forming gas feed holes 106 formed on the plasma-forming gas feedshower plate 107. By the structure, uniform feed of the plasma-forminggas to the plasma-forming space 109 in the plasma-forming chamber 108 isenabled.

As described above, the radicals generated from the plasma-forming gasare fed to the treatment chamber 113 via the radical feed holes 111formed on the plasma-confinement electrode plate 110 which partitionsthe treatment chamber 113 from the plasma-forming chamber 108. Only theelectrically neutral molecules or atoms such as radicals are allowed topass through the radical feed holes 111 formed on the plasma-confinementelectrode plate 110 to enter the treatment chamber 113 from theplasma-forming chamber 108, and very few ions in the plasma are allowedto pass therethrough to enter the treatment chamber 113. In theplasma-forming chamber 108, when the ion density is about 1×10¹⁰count/cm³, the ion density in the treatment chamber 113, calculated fromthe observed current level, is about 5×10² count/cm³. The value showsthat the ion density is decreased to one to ten million or less, whichmeans actually very few ions are allowed to enter the treatment chamber113. To the contrary, the radicals are transferred to the treatmentchamber 113 by about several percentages to about several tens ofpercentages, depending on the life, of the total quantity of radicalsgenerated in the plasma-forming chamber.

For the charged particles to act as plasma, the Debye length has to besufficiently shorter than the internal length of the apparatus. If theplasma exists at above-described ion density in the treatment chamber,and with the assumption of 1 to 5 eV of electron temperature, the Debyelength is calculated to about 0.3 to 0.7 m. Since, however, the internallength of actual semiconductor manufacturing apparatus is generally 0.3m or less at the maximum, the above ion density in the treatment chambersuggests that the charged particles in the treatment chamber have noproperty of plasma.

FIG. 4A illustrates the high-frequency applying electrode 104 in aplate-shape extending in the lateral direction in the plasma-formingchamber 108 given in FIG. 1, viewed from above the apparatus. FIG. 4B isa perspective view of the high-frequency applying electrode. Thehigh-frequency applying electrode 104 has a plurality of electrodethrough-holes 105 penetrating from the front face to the rear facethereof. The adopted through-holes 105 of the high-frequency applyingelectrode 104 are those having a shape given in FIG. 4A and FIG. 4B.Owing to the electrode through-holes 105, the electrode can uniformlydischarge even at a low power of 0.25 W/cm² or less, thus the radicalsare uniformly fed to the treatment chamber 113. The volume ratio of thevolume V2 of the electrode through holes 105 to the total volume V1 ofthe high-frequency applying electrode 104 including the electrodethrough holes 105, V2/V1, is preferably in a range from 0.01 to 0.8. Ina state of V2/V1 from 0.01 to 0.8, uniform discharge is attained asillustrated in FIG. 4C, thus the radicals are uniformly supplied to thetreatment chamber. If the total volume V2 of the plurality of electrodethrough-holes 105 is excessively small, or V2/V1<0.01, the segregateddischarge appears, as shown in FIG. 4D, to deteriorate the radicaldistribution. When V2/V1>0.8, discharge failed as shown in FIG. 4E tofail in supplying the radicals. To achieve stable and uniform radicaldistribution in small density of high frequency power, (from 0.001 to0.25 W/cm²), the ratio V2/V1 should at least be in a range from 0.01 to0.8, preferably from 0.04 to 0.37. The example selected the range from0.14 to 0.16.

The diameter of the plasma-forming gas feed hole 106 formed on theplasma-forming gas feed shower plate 107 is preferably 2 mm or smaller,and more preferably 1.5 mm or smaller. With the diameter of theplasma-forming gas feed hole 106 of 2 mm or smaller, and preferably 1.5mm or smaller, the uniformity of the surface treatment of the substrate5 significantly improved. As a result, it was found that the treatmenttime can be shortened. The phenomenon suggests that the radicals fromplasma generated in the above-described plasma-forming spaces 109 a and109 b and in the electrode through-hole 105 on the high-frequencyapplying electrode 104 can be stably and uniformly supplied to thesubstrate in the substrate cleaning treatment chamber 121. As for theminimum diameter of the plasma-forming gas feed hole 106, any value isapplicable if only the hole 106 has a function of allowing theplasma-forming gas to pass therethrough.

If the diameter of the plasma-forming gas feed hole 106 was larger than2 mm, the uniformity of surface treatment of the substrate 5significantly deteriorated. The worsened uniformity needed a longtreatment time. The phenomenon suggests that the uniform supply ofradicals to the substrate cleaning treatment chamber 121 was failed.

Examples of the shapes of 2 mm or smaller diameter of the plasma-forminggas feed hole 106 on the plasma-forming gas feed shower plate 107 aregiven in FIGS. 5A to 5E. FIGS. 5A to 5E illustrate the respectiveenlarged cross sections of the plasma-forming gas feed shower plate 107in the vicinity of the plasma-forming gas feed hole 106. As given inFIG. 5A, the plasma-forming gas feed hole 106 may be a vertical hole, oras given in FIGS. 5B and 5C, the plasma-forming gas feed hole 106 mayhave a spot-facing at one side thereof. The spot-facing may open to theside of plasma-forming space 109 a as shown in FIG. 5C, or may open toother side as shown in FIG. 5B. As shown in FIGS. 5D and 5E, theplasma-forming gas feed hole 106 may be in a tapered shape, givinglarger diameter thereof at the side of plasma-forming space 109 a thanthe diameter at other side, as shown in FIG. 5E, or giving smallerdiameter thereof at the side of plasma-forming space 109 a than thediameter at other side, as shown in FIG. 5D. The examples of the holeshape are the same for the case of 1.5 mm or smaller diameter of theplasma-forming gas feed hole 106.

FIG. 5F is a graph illustrating the effect of the plasma-forming gasfeed shower plate 107 in the example. The etching rate of silicon oxidefilm on the substrate placed in the treatment chamber was determinedunder the conditions of: HF gas as the plasma-forming gas at 100 sccm offlow rate; high frequency power density of 0.01 W/cm², and the internalpressure of the treatment chamber of 50 Pa. In FIG. 5F, the horizontalaxis is the position in the substrate face, and the vertical axis is theetching rate of silicon oxide film normalized by the etching rate atcenter of the substrate surface. As shown in FIG. 5F, when the case 901which applied the plasma-forming gas feed shower plate was compared withthe case 902 which did not apply the plasma-forming gas feed showerplate and applied lateral directional feed, as the feed method of therelated art, the case 901 of feeding through the shower plate gavebetter uniformity in the in-plane etching rate. Presumable cause of theresult is that the uniform gas feed to the plasma-forming space 109secured uniform concentration distribution of active species in theplasma-forming space 109, and the phenomenon contributed to the result.Consequently, together with the effect of uniform plasma-forming owingto through-holes 105 of a high-frequency applying electrode 104described below, there was confirmed further uniform radical supply tothe treatment chamber.

A method of manufacturing a semiconductor device using the film-formingapparatus 1 illustrated in FIG. 1 of the present invention will bedescribed below.

The description begins with a substrate treatment step as the firststep, and with the condition thereof. The apparatus used in the firststep is the substrate treatment apparatus 100 illustrated in FIGS. 3A to3D.

As the plasma-forming gas, HF at 100 sccm of the flow rate was suppliedto the plasma-forming chamber 108, thus generated plasma in theplasma-forming part. The radicals in the plasma were supplied to thetreatment chamber 113 via the radical feed holes 111 formed on theplasma-confinement electrode plate 110 for plasma separation providedwith the plurality of radical-passing holes 111. To suppress theexcitation energy of the radicals, HF as the treatment gas was suppliedto the treatment chamber 113 via the treatment gas feed holes 112 at aflow rate of 100 sccm. The high frequency power density for plasmageneration was 0.01 W·cm², the pressure was 50 Pa, the treatment timewas 5 min, and the temperature of the substrate 5 was 25° C. The plasmafor substrate cleaning treatment is generated at a high frequency powerdensity in a range from 0.001 to 0.25 W/cm², which range is aboutseveral tenth to one severals to that of the plasma in the case offilm-deposition treatment. Higher density of high frequency power thanthat level makes it difficult to conduct selective etching of nativeoxide film.

FIG. 12 shows the observed surface roughness after the first step of thepresent invention, with the comparison with the result of conventionaldry-treatment and wet-treatment. As shown in FIG. 12, the surfaceroughness Ra obtained from the first step of the present invention was0.18 nm, which is a good level almost equal to the surface roughness Raof 0.17 nm obtained by the wet-treatment (wet-cleaning) with a dilutehydrofluoric acid solution. For the case of not supplying the HF gas asthe treatment gas, the surface roughness Ra became 2.0 nm, which is alarge level. Furthermore, even when the treatment time was extended to10 minutes, the surface roughness Ra was confirmed to 0.19 nm, which isnot a rough level. The improved surface flatness owes to the selectiveremoval of the surface native oxide film and organic matter in relationto Si. Presumable mechanism is that the high excitation energy HFgenerated from plasma is brought to collide with the unexcited HFseparately fed as the treatment gas, thus forming HF having suppressedexcitation energy, and the suppressed excitation energy HF selectivelyremoves the surface native oxide film while not etching the Si atoms onthe surface. The observed results confirmed that the use of the presentinvention can realize the surface flatness, equivalent to that of thewet-cleaning, by the dry-cleaning which does not need the hightemperature pretreatment.

The condition to attain the surface flatness according to the presentinvention is only to form HF having suppressed excitation energy bymixing and colliding an HF having high excitation energy generated fromthe plasma with an unexcited HF separately fed as the treatment gas.Consequently, the structure of the example is not limited if only theabove condition is satisfied.

That is, according to this example, the radicals generated by the plasmaare supplied toward the substrate via the radical feed holes 111 as theplurality of through-holes formed on the plasma-confinement electrodeplate 110, while simultaneously supplying the treatment gas via theplurality of treatment gas supply holes formed on the electrode plate.From the point of uniformity, however, and specifically when uniformtreatment is required to a large diameter substrate, it is necessary tosupply both the radicals and the unexcited treatment gas uniformly tothe substrate. To this end, as in this example, it is preferable toadopt the structure which allows radicals to be shower-supplied from theelectrode plate facing the substrate, and allows also the treatment gasto be shower-supplied simultaneously.

Although the example conducts the radical generation by the plasmaformation by the high frequency application, the radical generation maybe done by the plasma formation by microwave and other methods.Specifically, there may also be applied the radical generation throughUV, X-ray, and microwave excitation given in FIG. 7, and thecatalyst-chemical excitation given in FIG. 8. In FIG. 7, UV, X-ray, andmicrowaves are irradiated to the plasma gas from a feed chamber 203 toturn the plasma gas into plasma. In FIG. 7, reference numeral 5signifies the substrate; 201, the plasma-forming gas supply system; 202,the plasma-forming gas supply pipe; 204, the plasma-confinementelectrode plate for plasma separation provided with the plurality ofradical-passing holes; 205, the radical feed hole; 206, the treatmentgas feed hole; 207, the treatment chamber; 208, the substrate holder;209, the treatment gas supply pipe; 210, the treatment gas supplysystem; and 211, the exhaust system. The treatment gas system has thesame structure with that of FIGS. 3A to 3D. FIG. 8 illustrates thestructure of turning the gas into plasma by a heating catalyst body 303.Reference numeral 5 signifies the substrate; 301, the plasma-forming gassupply system; 302, the plasma-forming gas supply pipe; 304, theplasma-confinement electrode plate for plasma separation provided withthe plurality of radical-passing holes; 305, the radical feed hole; 306,the treatment gas feed hole; 307, the treatment chamber; 308, thesubstrate holder; 309, the treatment gas supply pipe; 310, the treatmentgas supply system; and 311, the exhaust system. The treatment gas systemhas the same structure with that of FIGS. 3A to 3D.

Regarding the plasma-forming gas fed to the plasma-forming chamber, theexample used only HF. The plasma-forming gas is only required to containat least HF, and specifically HF diluted with Ar may be used. Bygenerating plasma, and by passing the plasma through theplasma-confinement electrode plate 110, the radicals enter the treatmentchamber 113. For the treatment gas entering the treatment chamber 113,the example used only HF. The treatment gas is only required to containat least HF, and specifically HF diluted with Ar may be used. By mixingthe radicals which were fed to the treatment chamber 113 via the radicalfeed holes 111 formed on the plasma-confinement electrode plate 110 withthe treatment gas fed from the treatment gas feed holes 112, there iscreated an atmosphere in which the excitation energy of radicals issuppressed. Then, the native oxide film and the organic matter on thesurface of the substrate are selectively removed in relation to Si ofthe substrate material, thereby performing the substrate surfacetreatment while suppressing the surface roughening.

FIG. 13 is a graph of dependency of the surface roughness (Ra) on the HFfraction in the treatment gas, comparing the case of plasma gascontaining HF according to the present invention with the case of plasmagas made only of Ar in the related art.

According to Japanese Patent Laid-Open No. 10-172957 of the related art,the oxide film was able to be selectively removed by a mixed gas of:argon, helium, xenon, and hydrogen which are excited by a remote plasmasource; and HF gas fed in downstream side, and that no damage wasobserved on the silicon substrate. The removal, however, did not satisfythe flatness level required in recent years. The expression of HFfraction in the plasma-forming gas, HF/(HF+Ar)=0, signifies the case ofrelated art using sole Ar gas as the plasma-forming gas. As shown inFIG. 13, compared with the case of sole Ar as the plasma-forming gas inthe related art, or HF/(HF+Ar)=0, the case of the present invention ofcontaining HF in the plasma-forming gas provides significantly goodsurface roughness (Ra). Varied mixing ratio of HF to Ar in theplasma-forming gas and in the treatment gas varied the surface roughnessafter removing the native oxide film. It was found that the HF fractionin the plasma-forming gas to the total gas flow rate of theplasma-forming gas is preferably in a range from 0.2 to 1.0, and furtherto attain the surface roughness of 0.5 nm or smaller equivalent to thesurface roughness after the wet-cleaning, the HF fraction thereto ispreferably in a range from 0.6 to 1.0. The surface roughness afterremoving the native oxide film became minimum, or became flat, in thecase of sole HF of the plasma-forming gas and of the treatment gas.

Even for the case that HF gas was used as the plasma-forming gas to besupplied to the plasma-forming chamber 108, and that the radicals weresupplied via the plurality of radical feed holes 111 formed on theplasma-confinement electrode plate 110 for plasma separation providedwith a plurality of radical-passing holes 111, when the treatment gaswas composed only of Ar, the native oxide film on the surface of thesubstrate was not able to be removed, and failed to attain the object ofthe surface treatment. For the case that HF gas was used as theplasma-forming gas and that no gas was supplied as the treatment gas,the surface roughness Ra became 2.5 nm, which was worse than the case ofusing HF as the treatment gas.

The example used a Si substrate. However, the substrate surfacetreatment of the present invention does not limit to the surfacetreatment of Si substrate. In concrete terms, the request is only tostructure the substrate surface with a group IV semiconductor such as Siand SiGe. More specifically, the substrate surface treatment can beapplied to the one for removing native oxide film and organiccontamination on the surface of group IV semiconductor such as thin Silayer which is adhered to or deposited on a glass substrate.

The high frequency power density applied onto the high-frequencyapplying electrode 104 is preferably in a range from 0.001 to 0.25W/cm².

FIG. 6 shows the dependency of the native oxide film/Si, (etching rateratio of native oxide film to Si), on the high frequency power densityfor the case of using HF gas as the plasma-forming gas and using HF asthe treatment gas. Decrease in the high frequency power densitysuppresses the Si etching, and thus only the native oxide film isselectively etched. The value of the amount of etching the native oxidefilm divided by the amount of etching the Si is defined as “native oxidefilm/Si”. Decrease in the high frequency power density relativelydecreases the amount of etching of Si so that the “native oxide film/Si”increases. On the other hand, increase in the high frequency powerdensity significantly increases the etching of Si, thus decreasing the“native oxide film/Si”. Increase in the high frequency power densityinduces the etching of Si, which roughens the surface. To decrease thesurface roughening, it is necessary to increase the “native oxidefilm/Si” and to decrease the high frequency power density. To this end,the high frequency power density is selected to above range of from0.001 to 0.25 W/cm², preferably from 0.001 to 0.125 W/cm², and mostpreferably from 0.001 to 0.025 W/cm².

Then, the description is given to the Si and SiGe epitaxial singlecrystal growth step as the second step, and to the condition thereof.

The description is for the process in which the first step is conductedusing the film-forming apparatus 1 given in FIG. 1 and using the surfacetreatment apparatus 100 given in FIGS. 3A to 3D to remove the nativeoxide film formed on the Si substrate, and then the substrate istransferred to a CVD apparatus 20 via the vacuum transfer chamber 60 toconduct the second step, where the growth of Si and SiGe single crystalfilm proceeds on the treated surface of the substrate.

The substrate was treated on the surface thereof in the first step, andthen was treated in the CVD apparatus 20 as the second step under thecondition of: substrate temperature of 600° C., Si₂H₆ supply at 36 sccm,pressure holding at 2E-3 Pa, for 3 minutes. After that, the substratewas treated therein under the condition of: substrate temperature of600° C., Si₂H₆ and GeH₄ supply at 36 sccm, respectively, pressureholding at 4E-3 Pa, for 3 minutes. Thus treated substrate gave a surfaceroughness of the SiGe single crystal growth on the Si equivalent to thesurface roughness of the substrate treated by wet-cleaning using adiluted hydrofluoric acid, providing a good SiGe single crystal film, asshown in FIG. 14. As given in FIG. 15, compared with the case ofwet-cleaning followed by the above Si/SiGe growth, the case of thisexample gave smaller atom density of oxygen and carbon at the interfacebetween the Si substrate and the grown Si. In concrete terms, the atomdensity of oxygen and carbon at the interface was 2×10²⁰ atoms/cm³ orless. The phenomenon owes to the suppress of adsorption of oxygen andcarbon impurities onto the surface by the vacuum transfer of thesubstrate without exposing thereof to atmospheric air after cleaning. Inthe process of growth of Si and SiGe single crystal film in the CVDapparatus 20, there can be used: a hydrogenated gas such as Si₂H₆ andGeH₄; a mixture of a hydrogenated gas with a doping material gas such asB₂H₆, PH₃, and AsH₃; or SiH₄ instead of Si₂H₆.

The description is given to the dielectric film sputtering film-formingstep as the third step, the oxidation-nitrification step of the formeddielectric film as the fourth step, and the electrode sputtering step asthe fifth step. Succeeding to the second step, the substrate issubjected to a process to manufacture the FET device. The processincludes: the third step of sputtering film-formation of the dielectricmaterial in a sputtering apparatus 40 via the transfer chamber 60; thefourth step of transferring the substrate through the transfer chamber60 to the oxidation-nitrification apparatus 30 to oxidize the dielectricmaterial therein; and the fifth step of transferring the substratethrough the transfer chamber 60 to the sputtering apparatus 40 tosputter the metal electrode material therein. The apparatus 10 through50 are each controlled by the respective transfer or process controllers70 through 74.

The dielectric material film-forming in the third step may be conductedby CVD other than sputtering. Similarly, the film-forming of metalelectrode material in the fifth step may be conducted by CVD other thansputtering.

With the surface treatment apparatus 100 illustrated in FIG. 3A, thefirst step was conducted to remove the native oxide film, and the secondstep was conducted to grow the Si single crystal film. Then, thesubstrate 5 passed through the vacuum transfer chamber 60 to enter thedielectric-electrode sputtering apparatus 40 without being exposed toatmospheric air, where the sputtering film-formation of Hf wasconducted, and the substrate was transferred to theoxidation-nitrification apparatus 30 via the vacuum transfer chamber 60to oxidize the formed dielectric material film without exposing thesurface of the dielectric material to atmospheric air, thus conductedplasma and radical oxidation. Furthermore, the substrate 5 wastransferred to the dielectric-electrode sputtering apparatus 40 via thevacuum transfer chamber 60 without being exposed to atmospheric air,thus sputtered to form the film of TiN electrode. The characteristics ofthe obtained device were evaluated. The data are given in FIG. 16, FIG.17, and FIG. 18.

FIG. 15 shows a C-V curve drawn by measuring the capacitance of a sampleprepared by the present invention and by the related art (wet-cleaningwas applied instead of the first step), respectively, applying voltageto the electrode part. Compared with the sample of the related art whichprovided hysteresis of about 30 mV, the sample of the present inventionattained good result of 10 mV of hysteresis.

FIG. 17 shows a comparison of the interface state density and the fixedcharge density, between those obtained by the present invention andthose obtained in the related art (wet-cleaning was applied instead ofthe first step). Samples were prepared by the process of the presentinvention to determine the C-V curve, from which curve the interfacestate density and the fixed charge density were calculated. Both theinterface state density and the fixed charge density were smaller thanthose in the related art because of the small quantity of oxygen andcarbon impurities on the surface of Si film formed by the second stepafter the substrate cleaning in the first step, as shown in FIG. 15. Thephenomenon is the effect of continuous treatment in vacuum after thedry-cleaning.

The film-forming apparatus 1 illustrated in FIG. 1 has a controller toconduct entire process in vacuum for each process apparatus and for eachtransfer apparatus. That is, a transfer controller receives the inputsignal, generated from the apparatus concerned, at input part, runs thetransfer program which was programmed so as to operate according to theflowchart on the processor, and thus outputs the action command fortransferring the substrate to each process apparatus to the concernedapparatus via the vacuum transfer. Process controllers A 71 through D 74receive the input signal from the process apparatus, run the programwhich was programmed so as to operate the treatment according to theflowchart, and thus output the action command to the apparatusconcerned. The structure of the controller 70 or 71 to 74 is the onegiven as the reference numeral 81 in FIG. 2, composed of an input part82, a memory part 83 having a program and data, a processor 84, and anoutput part 85. The structure is basically a computer structure, whichcontrols the concerned apparatus.

FIG. 10 illustrates the control of the transfer controller 70 and theprocess controllers A to D (71 to 74). In Step 610, a Si substrate withnative oxide film formed thereon is prepared. The transfer controller 70generates a command to bring the vacuum in the load-lock apparatus 40 to1 Pa or below, (Step 611). Further the transfer controller generates acommand to bring the vacuum in the surface treatment apparatus 100 to1E-4 Pa or higher vacuum level, and then moves the substrate 5 into thesurface treatment apparatus 100 via the transfer chamber 60 to place thesubstrate on the substrate holder. The process controller A71 controlsthe procedure of above-described first step of applying surfacetreatment to the substrate 5, (Step 613).

The transfer controller 70 controls the CVD film-forming apparatus 20 toevacuate to establish the vacuum of 1E-4 Pa or lower vacuum level, andthen moves the substrate 5 from the surface treatment apparatus 100 tothe CVD film-forming apparatus 20 to place the substrate 5 therein viathe transfer chamber 60.

The process controller B72 controls the above-described second step oftreating single crystal growth in the CVD film-forming apparatus 20,(Step 615). Immediately after that, the process controller B72 moves thesubstrate into the dielectric-electrode sputtering apparatus 40 via thetransfer chamber 60 to conduct the third step of dielectric-electrodesputtering film-forming (Step 616).

The process controller C73 controls the third step of film-formingtreatment in the dielectric-electrode sputtering apparatus 40 (Step617). The transfer controller 70 establishes the vacuum of 1E-4 Pa orlower vacuum level in the oxidation-nitrification apparatus 30, andmoves the substrate 5 from the dielectric-electrode sputtering apparatus40 to the oxidation-nitrification apparatus via the transfer chamber 60(Step 618). The process controller D74 conducts control to execute thefourth step in the oxidation-nitrification apparatus 30 (Step 619).Immediately after that, the process controller D74 moves the substrate 5to the dielectric-electrode sputtering apparatus 40 via the transferchamber 60 to conduct the fifth step of metal electrode sputteringfilm-forming (Step 620). The process controller C73 conducts control toexecute film-forming treatment of example 3 in the dielectric-electrodesputtering apparatus 40 (Step 621). Then, the transfer controller 70opens the transfer chamber 60 to atmospheric air using the load-lockapparatus 50 (Step 622).

By the above-described treatment of the present invention, the MOS fieldeffect transistor (FET) 90 illustrated in FIG. 19 was manufactured. AnHfO film was adopted as a dielectric gate insulation film 95 below agate electrode 94 between a source region 92 and a drain region 93 of aSi substrate 91. Other than HfO, preferable gate insulation film 95includes a film of Hf, La, Ta, Al, W, Ti, Si, Ge, or an alloy thereof,and more specifically there are applicable HfN, HfON, HfLaO, HfLaN,HfLaON, HfAlLaO, HfAlLaN, HfAlLaON, LaAlO, LaAlN, LaAlON, LaO, LaN,LaON, HfSiO, and HfSiON. The relative permittivity thereof is in a rangefrom 3.9 to 100, and the fixed charge density is in a range from 0 to1×10¹¹ cm⁻². The film thickness of the gate insulation layer is set to arange from 0.5 to 5.0 nm.

The term “fixed charge” is also referred to as “fixed oxide filmcharge”, meaning the charge existing in SiO₂ film and being fixedtherein, not migrating in electric field or the like. The fixed oxidefilm charge appears caused by a structural defect in the oxide film, anddepends on the formed state of the oxide film or the heat treatmentthereof. Normally there exists a positive fixed charge in the vicinityof Si—SiO₂ interface originated from a dangling bond of Si in silicon.The fixed oxide film charge makes the C-V characteristic of MOSstructure shift in parallel along the gate voltage axis. The fixedcharge density is determined by the C-V method.

As the gate electrode 94 of MOS-FET in FIG. 19, there are applied: metalsuch as Ti, Al, TiN, TaN, and W; polysilicon (B(boron)-dope: p-Type orP(phosphorus)-dope: n-Type); and Ni-FUSI (fully silicide).

The semiconductor/insulation film joint, which was prepared by themethod of the present invention, that is, by the method of treating thesurface of a Si substrate having native oxide film formed thereon,growing the Si single crystal film without exposing thereof toatmospheric air, sputtering for forming a dielectric film such as Hfwithout exposing the substrate to atmospheric air, and oxidizing andnitrifying thereof, gives smaller fixed charge and lower interface statethan those of the joint prepared in the atmospheric transfer. Therefore,the joint gives a C-V curve with small hysteresis as shown in FIG. 16,with small leak current, thereby providing good device characteristics.The term “interface state” signifies the energy level of electron beingappeared on interface of joint of different kinds of semiconductors andon interface of joint between a semiconductor and a metal or aninsulation material. Since the semiconductor face on the interfacebecomes a condition of breaking bond between atoms, there appears anon-bonding condition called the dangling bond, thus creating an energylevel to allow entrapping the charge. Also impurity or defect on theinterface creates an energy level allowing entrapping the charge, or aninterface state. Generally the interface state shows a long responsetime and is instable, thus often adversely affects the devicecharacteristics. Lower interface state means better interface. Theinterface state density is determined by the C-V method.

As illustrated in FIG. 1, the film-forming apparatus of the presentinvention uses the configuration having each one of: the surfacetreatment unit 100, the CVD film-forming unit 20, thedielectric-electrode sputtering unit 30, the oxidation-nitrificationunit 40, the load-lock chamber 50, and the transfer chamber 60. However,the quantity of each of those units is not necessarily one, and morethan one unit for thereeach can be applied depending on the throughput,the film structure, and the like. For example, to increase thethroughput, the load-lock chamber may be substituted by a plurality ofload-lock chambers allotting the functions of loading and unloading toeach one. Furthermore, for example, the sputtering unit 30 may besubstituted by two or more sputtering units allotting the functions offorming the dielectric film and forming the electrode to each one.

However, for effective use of the substrate treatment method whichallows conducting the dry substrate surface treatment while keeping flatsurface according to the present invention, it is preferable to have atleast one unit for each of the surface treatment unit 100, the CVDfilm-forming unit 20, the load-lock chamber 50, and the transfer chamber60. With this configuration, the presence of load-lock chamber makes thedry substrate surface treatment possible at high throughput in a stableevacuated atmosphere, and the film-forming by transferring the substrateto the CVD film-forming unit via the transfer chamber in a vacuumwithout exposing the substrate to atmospheric air allows keeping goodcondition of interface between the Si substrate surface and the CVDfilm-formed Si/SiGe layer.

In addition, to effectively use the substrate treatment method whichallows treating the dry substrate surface while keeping flat surfaceaccording to the present invention, it is preferable to have at leastone unit for each of the surface treatment unit 100, thedielectric-electrode sputtering unit 30, the load-lock chamber 50, andthe transfer chamber 60. With this configuration, the presence ofload-lock chamber makes the dry substrate surface treatment possible athigh throughput in a stable evacuated atmosphere, and the film-formingby transferring the substrate to the dielectric-electrode sputteringunit 30 via the transfer chamber in a vacuum without exposing thesubstrate to atmospheric air allows keeping good condition of interfacebetween the Si substrate surface and the dielectric film or conductivefilm as the base of the insulation film prepared by sputtering on the Sisubstrate surface.

Although the example does not give the detail of the CVD film-formingunit 20 in the drawing, any type of epitaxial film-forming unit isapplicable if only the unit is provided with a chamber, asubstrate-heating mechanism for heating both the substrate holder forholding the substrate and the substrate held thereto, a gas-feedmechanism for supplying a gas containing the raw material gas to conductthe CVD film-formation, and an exhaust means for discharging the chamberatmosphere.

Similarly, the detail of the sputtering unit 30 is not given in thedrawing. The sputtering unit 30 may be, however, any type if only theunit has a chamber, a substrate holder for holding the substrate, amechanism for feeding the gas into the chamber, an exhaust means fordischarging the chamber atmosphere, a sputtering cathode for mountingthe target made of dielectric or conductive metal, and a high frequencypower supply mechanism or a direct current power supply mechanism.

The quantity of the sputtering cathode for mounting the target made ofdielectric or conductive metal, (not shown), in the sputtering unit 30is not necessarily one, and a plurality of sputtering cathodes may beapplied for forming a plurality of continuous or discontinuous films andfor mounting a plurality of targets thereon. From the point ofuniformity of the thickness distribution of the formed film, thesubstrate holder is preferably provided with a rotary mechanism torotate the mounted substrate. For allowing film-forming by reactivesputtering, the gas-feed mechanism of the sputtering unit 30 preferablyfeeds not only inert gas such as Ar but also a reactive gas such as N₂and O₂, or a mixture of reactive gas with Ar gas.

1.-2. (canceled)
 3. A substrate cleaning method of cleaning an oxidefilm on the surface of a semiconductor substrate placed in asubstrate-cleaning treatment chamber, the method comprising the stepsof: feeding a plasma-forming gas to a plasma-forming chamber via aplasma-forming gas feed shower plate, the plasma-forming gas feed showerplate being arranged in the plasma-forming chamber and being grounded;exciting the plasma-forming gas to generate plasma in the plasma-formingchamber by applying a power from a high-frequency power source to ahigh-frequency applying electrode, the high-frequency applying electrodebeing arranged between a plasma-confinement electrode plate and theplasma-forming gas feed shower plate, the plasma-confinement electrodeplate partitioning the plasma-forming chamber from thesubstrate-cleaning treatment chamber and being grounded; selectivelyfeeding a radical in the plasma from the plasma-forming chamber to thesubstrate-cleaning treatment chamber via a plurality of plasma feedholes formed distributedly on the face of the plasma-confinementelectrode; feeding an unexcited treatment gas into thesubstrate-cleaning treatment chamber; and conducting cleaning treatmentof the oxide film on the surface of the semiconductor substrate by themixed atmosphere of the radical and the treatment gas, fed intosubstrate-cleaning the treatment chamber, wherein the treatment gas isfed into the substrate-cleaning treatment chamber from the face of theplasma-confinement electrode, in almost parallel with the radicalfeeding, via a plurality of treatment gas feed holes formed next to atleast a part of the radical feed holes of the plasma-confinementelectrode.
 4. A substrate cleaning method according to claim 3, whereinthe semiconductor substrate is a Si substrate, and the Si substrate iscleaned by etching to remove the oxide film on the Si substrate.
 5. Amethod of forming a gate insulation film in a MOS structure, comprisingthe steps of: cleaning the surface of a Si substrate by the method ofclaim 4; moving the surface-cleaned Si substrate to an epitaxial chamberwithout exposing the Si substrate to atmospheric air to form anepitaxial layer on the surface-cleaned Si substrate in the epitaxialchamber; moving the Si substrate having the epitaxial layer formedthereon to a sputtering chamber without exposing the Si substrate toatmospheric air to form a dielectric film by sputtering on the epitaxiallayer; and moving the Si substrate having the dielectric film formedthereon to an oxidation-nitrification chamber without exposing the Sisubstrate to atmospheric air to form the gate insulation film byoxidizing, nitrifying or oxynitrifying the dielectric film.
 6. A methodof claim 5, wherein the dielectric film is made of the one selected fromthe group consisting of Hf, La, Ta, Al, W, Ti, Si and Ge, or an alloythereof.
 7. A method of cleaning a substrate surface in a substratecleaning apparatus including a plasma-forming chamber, asubstrate-cleaning treatment chamber, and a plasma-confinement electrodeplate partitioning the plasma-forming chamber from thesubstrate-cleaning treatment chamber, the method comprising the stepsof: placing a plate-shape substrate facing the face of theplasma-confinement electrode plate in the substrate-cleaning treatmentchamber; feeding a radical in the plasma generated in the plasma-formingchamber from the plasma chamber to the substrate-cleaning treatmentchamber via a plurality of radical feed holes distributedly formed onthe face of the plasma-confinement electrode plate for communicating theplasma-forming chamber with the substrate-cleaning treatment chamber;and feeding an unexcited treatment gas into the substrate-cleaningtreatment chamber, wherein a high-frequency power with a high frequencypower density ranging from 0.001 to 0.25 W/cm² is applied to ahigh-frequency applying electrode in a plate-shape arranged to face theplasma-confinement electrode plate in the plasma-forming chamber andextending in a lateral direction in the plasma-forming chamber, whereinthe high-frequency applying electrode has a plurality of through-holesformed penetrating from the front face to the rear face thereof, and aratio of V2/V1 is set in a range from 0.01 to 0.8 (where V1 is the totalvolume of the high-frequency applying electrode including thethrough-holes, and V2 is the total volume of the through-holes); andwherein the feed of the treatment gas to the substrate-cleaningtreatment chamber is done, in parallel with the radical feeding, througha plurality of treatment gas feed holes formed so as to face the face ofthe substrate, next to at least a part of the radical feed holes of theplasma-confinement electrode.
 8. A method of cleaning a substratesurface according to claim 7, wherein an oxide film on the substratesurface is cleaned.
 9. A method of cleaning a substrate surfaceaccording to claim 8, which is a method of cleaning an oxide film on thesurface of a group IV semiconductor material substrate, wherein plasmais generated by feeding a plasma-forming gas containing HF to theplasma-forming chamber, and the treatment gas contains HF.
 10. A methodof cleaning a substrate surface according to claim 9, wherein the HFfraction to the total gas flow rate of the plasma-forming gas is in arange from 0.2 to 1.0.
 11. A method of cleaning a substrate surfaceaccording to claim 10, wherein the treatment gas is sole HF.
 12. Amethod of cleaning a substrate surface according to claim 7, wherein theplasma gas is fed to the plasma-forming chamber via a shower plate, theshower plate has an inner face facing the high-frequency applyingelectrode, and the plasma-forming gas is fed to the plasma-formingchamber via a plurality of plasma-forming gas feed holes distributedlyformed on the inner face of the shower plate.
 13. A method of forming agate insulation film in a MOS structure, comprising the steps of:cleaning an oxide film on the surface of a Si substrate by the method ofclaim 9; moving the surface-cleaned Si substrate to an epitaxial chamberwithout exposing the Si substrate to atmospheric air to form anepitaxial layer on the surface-cleaned Si substrate; moving the Sisubstrate having the epitaxial layer formed thereon to a sputteringchamber without exposing the Si substrate to atmospheric air to form adielectric film on the epitaxial layer by sputtering; and moving the Sisubstrate having the dielectric film formed thereon to anoxidation-nitrification chamber without exposing the Si substrate toatmospheric air to form the gate insulation film by oxidizing,nitrifying or oxynitrifying the dielectric film.
 14. A method of forminga gate insulation film according to claim 13, wherein the dielectricfilm is made of the one selected from the group consisting of Hf, La,Ta, Al, W, Ti, Si and Ge, or an alloy thereof.
 15. A substrate cleaningmethod according to claim 3, wherein the treatment gas is a cleaning gasthat cleans the substrate.
 16. A method of cleaning a substrate surfaceaccording to claim 7, wherein the treatment gas is a cleaning gas thatcleans the substrate.
 17. A substrate cleaning method according to claim3, wherein each of the plasma-forming gas and the treatment gas is an HFgas.
 18. A method of cleaning a substrate surface according to claim 7,wherein a plasma-forming gas is fed to the plasma-forming chamber via aplasma-forming gas feed shower plate connected to the plasma-forming gassupply system.
 19. A method of cleaning a substrate surface according toclaim 18, wherein each of the plasma-forming gas and the treatment gasis an HF gas.